Rev. bras. ortop. vol.49 número5

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Original

Article

Description

of

an

evaluation

system

for

knee

kinematics

in

ligament

lesions,

by

means

of

optical

tracking

and

3D

tomography

夽

,

夽夽

Tiago

Lazzaretti

Fernandes

,

Douglas

Badillo

Ribeiro

,

Diogo

Cristo

da

Rocha

,

Cyro

Albuquerque

_,

_César

_Augusto

_Martins

_Pereira

_,

_André

_Pedrinelli

_,

Arnaldo

José

Hernandez

a_{InstituteofOrthopedicsandTraumatology,HospitaldasClínicas,MedicalSchool,UniversidadedeSãoPaulo,SãoPaulo,SP,Brazil}

b_{DepartmentofMechanicalEngineering,UniversityCenterofFundac¸ãoEducacionalInaciana(FEI),SãoBernardodoCampo,SãoPaulo,}

SP,Brazil

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t

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o

Articlehistory:

Received29August2013 Accepted3October2013 Availableonline28August2014

Keywords: Kneejoint

Anteriorcruciateligament X-raycomputedtomography

a

b

s

t

r

a

c

t

Objective:Todescribeanddemonstratetheviabilityofamethodforevaluatingknee kine-matics,bymeansofacontinuouspassivemotion(CPM)machine,beforeandafteranterior cruciateligament(ACL)injury.

Methods:Thisstudywasconductedonakneefromacadaver,inamechanicalpivot-shift simulator,withevaluationsusingopticaltracking,andalsousingcomputedtomography. Results:Thisstudydemonstratedtheviabilityofaprotocolformeasuringtherotationand translationoftheknee,usingreproducibleandobjectivetools(error<0.2mm).The mech-anizedprovocationsystemofthepivot-shifttestwasindependentoftheexaminerand alwaysallowedthesameangularvelocityandtractionof20Nthroughoutthemovement. Conclusion: Theclinicalrelevanceofthismethodliesinmakinginferencesabouttheinvivo behaviorofakneewithanACLinjuryandprovidinggreatermethodologicalqualityinfuture studiesformeasuringsurgicaltechniqueswithgraftsinrelativelyclosepositions.

©2014SociedadeBrasileiradeOrtopediaeTraumatologia.PublishedbyElsevierEditora Ltda.Allrightsreserved.

Descric¸ão

de

sistema

de

avaliac¸ão

da

cinemática

do

joelho

em

lesões

ligamentares

a

partir

de

rastreamento

óptico

e

tomografia

3D

Palavras-chave: Articulac¸ãodojoelho Ligamentocruzadoanterior

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e

s

u

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o

Objetivo:Descreveredemonstraraviabilidadedeummétododeavaliac¸ãodacinemáticado joelho,pormeiodeumaparelhodeCPM(continuouspassivemotion),anteseapósalesãodo ligamentocruzadoanterior(LCA).

夽

Pleasecitethisarticleas:FernandesTL,RibeiroDB,daRochaDC,AlbuquerqueC,PereiraCAM,PedrinelliAetal.Descric¸ãode sis-temadeavaliac¸ãodacinemáticadojoelhoemlesõesligamentaresapartirderastreamentoópticoetomografia3D.RevBrasOrtop. 2014;49(5):513–19.

夽夽

WorkdevelopedattheInstituteofOrthopedicsandTraumatology,HospitaldasClínicas,MedicalSchool,UniversidadedeSãoPaulo, SãoPaulo,SP,Brazil.

∗ _{Correspondingauthor.}

E-mail:tiago.lazzaretti@usp.br(T.L.Fernandes). http://dx.doi.org/10.1016/j.rboe.2014.08.005

Introduction

Anteriorcruciateligament(ACL)reconstructionisoneofthe orthopedics’surgicalproceduresmostperformedtoday.Ithas beenestimatedthatapproximately200,000suchprocedures areperformedintheUSAeveryyear.1

Despite the large number of studies that have been conductedin relation to ACL reconstruction,2,3 _{the rate of} excellentorgoodresultsrangesfrom69%to95%.4 Unsatisfac-toryresultsmayresultfrompersistentinstabilityoftheknee andconsequentdifficultyinreturningtothepreviouslevelof physicalactivity.5–9

ACLinsufficiencyisrepresentedbyanteriortranslationof thetibiaandbyrotationalinstabilityoftheknee.10_Thepivot shifttestisusedtoevaluatetherotationalstabilityoftheknee afterACLinjury.11_{Someauthorshavedemonstratedthatthe} presenceofapositivepivotshifttestispredictivefor develop-mentofosteoarthrosisandpoorfunctionalresults.12–15

Althoughthepivotshifttestisveryspecific(closeto100% under anesthesia),16–19 _{its resultis subjective because it is} examiner-dependent.Therefore,itistooimpreciseforusein scientificstudies.10,15,18–21

Musahletal.20 _{demonstratedthatthemechanizedpivot} shifttest,whichconsistsofusingacontinuouspassivemotion (CPM) machine to perform combined knee movements of internalrotation,valgusrotationandflexion,hasgreater accu-racythanthemanualtest.

Inconjunction with computer-assistedsurgerysystems, thepivotshiftsystemcanbemeasuredsatisfactorilyandbe usedtoanalyzekneestabilityafterdifferentACL reconstruc-tiontechniques.10,22

Thus,thepresentstudyhadtheobjectiveofdescribinga methodforkinematicevaluationofthekneebeforeandafter ACLinjury,bymeansoftechnologiesthatmakeitpossibleto objectivelyassesskneeligamentstability.23

For this, we present below the mechanized pivot shift apparatusandanopticaltrackingsysteminassociationwith computedtomography.

Materials

and

methods

Thisexperimentwasconductedonaknee fromacadaver, inconformitywithapprovalfromourinstitution’sResearch

EthicsCommittee.Thecadaver’sentirelowerlimbwasused, withpreservationofthehipandanklejoints.

Asinclusioncriteria,thekneeselecteddidnotpresentany previousACLinjuryorotherligamentinjuries,therewasno moderateorsevereosteoarthrosisandtherewasnoevidence offracturingordisplacedalignmentofthemechanicalaxisof thelimb.

Beforetheexperimentwasstarted,deinsertionandmuscle sectioningwereperformedinordertoenablefullkneerange ofmotion,asfollows:tenotomyoftheadductormassatits origininthepubis;sectioningofthequadricepsandhamstring musclesattheirorigin;andtenotomyofthecalcanealtendon.

Instrumentedpivotshiftandrotationalstabilityofthe knee

The mechanical pivot shift simulator was developed in the BiomechanicsLaboratory(LIM-41),startingfrom aCPM machine(Carci,Ortomed4060;ANVISA:10314290029)similar tothemodelusedandvalidatedbyBedietal.24

Thepelviswasstabilizedonthesurgicaltableandthehip andkneewereallowedtohavefullrangesofmotion.No sup-portusingbandsandthefemurortibialevelwasprovided.

TheCPMdevicewasdesignedtoallow15◦_{ofinternalankle}

rotation,forboththeleftandfortherightlowerlimbs.Axial compressionoftheanklewasperformedatanangularvelocity of1.62◦_{/s,frommaximumextensionto50}◦_{ofkneeflexion}20

(Fig.1).

Themomentofinternalandvalgusrotationofthekneewas determinedbymeansofasystemofcablesandpulleys cou-pledtotheCPMdevice.Thepointoftractiononthetibiawas definedbymeansofatitaniumpinfixedperpendicularlyto thetuberosityoftibia,oflength10cm.Thetractionofthe tita-niumpinwasperpendiculartotheaxisofthetibiaandhadthe sameforcevectorof20N25_{throughouttheflexion–extension} movement(0–50◦₎20_(Fig.2).

Measurementoftheanteriortranslationofthetibia

Fig.1–Mechanizedpivotshiftsystem.

Theverticalforce applied,inaccordance withthestudy by Bedietal.,26_{was68Nwiththekneeflexedat30}◦_.

Opticaltrackingsystem

Thetrackingsystem(MicronTracker 2,model H40) madeit possibletoobtainthespatialpositioningofthefemurandtibia throughidentifyingopticalmarkersanddeterminingtheknee translationandrotationmovements.

ThreeopticalmarkersweredistributedalongtwoL-shaped acrylicpiecesandwerefixedtothefemurandtibiausingtwo titaniumpins,inordertocreatearigidsystem(Fig.3).

Acomputerroutinewas developed(usingthe manufac-turer’slibrary,intheBasiclanguage)inordertorecognizeand savethethree-dimensionaldata(XYZ)thatwascapturedby thecamerasoftheopticaltrackingsysteminrealtime(15Hz, withmeasurementprecisionof0.2mm,accordingtothe man-ufacturer)(Fig.4).

Thecentralpointoftheknee,whichwasusedasa refer-encepointforcalculatingthekneerotationandtranslation,

Fig.2–Tractionsystemusingcablesandpulleys.

Fig.3–L-shapedopticalmarkersonthefemurandtibia.

wasdefinedfromcomputedtomographyontheentirelimb afterthetestshadbeenfinished(Fig.5).

For there to be correspondence between the optical trackingsystemandthecomputed tomography,radiodense filamentswereincludedinthecentralpositionsoftheoptical markers(Fig.6).

The knee movement was calculated from rotation and translationmatricesbetweenthecoordinatesystemsofthe camera and tomography and the coordinate systems pos-itionedonthebariummarkersandonthecenteroftheknee. Atthispoint,coordinatesystemswerecreatedforthetibia andfemur.Oneoftheaxescoincidedwiththerespectiveaxis ofeachbone:onehorizontalandtheothervertical.Thesetwo coordinatesystemsweredetermined,foreachtimeinstant, bythecoordinatesystemsofthemarkers.

Therotationaroundtheaxesandthetranslationofthe cen-tralpointofthekneewereobtainedbymeansoftherotation andtranslationmatrixbetweenthefemoralandtibial coordi-natesystems.ThisprocedurewasdevelopedusingtheGNU Octavecomputersoftware.

Protocol

The testswere carried out in twostages: before and after dissection,underdirectviewingoftheACLatitsoriginand insertion.

Ateachstage,threemeasurementsoftheanterior trans-lationofthetibiaweremadeusingamanualdynamometer (68N) and three measurements of knee flexion–extension were made using the mechanizedpivotshift, asdescribed earlier.

Results

The knee used was the right knee of a 45-year-old male cadaver.

Fig.4–Three-dimensionalidentificationoftheopticalmarkers.

Fig.5–Mechanicalaxisofthelowerlimb:three-dimensionalpointsatthecenterofthefemoralheadandankle. Radiodenseandopticalmarkersonthefemurandtibia.

Theincreaseinthedistancebetweenthepositionsofthe centerofthefemurandthecenterofthetibia,between maxi-mumextensionandmaximumflexionofthekneerepresents thepivotshiftphenomenon(Fig.8,redline).

Fig.9showstheanteriortranslationofthetibiawiththe kneeflexedat30◦_{inrelationtothefemur,beforeandafter68N}

or15lb25_{oftractionthroughthetitaniumpin,perpendicularly} tothetibia.

140 120 100 80 60 40 20 0

−20

90 95

100 105

110 115

120

760 750 740 730 720 710 700 690 680 670 660 650 125

y

x Tibia

Femur

z

Fig.7–Graphicalrepresentationofkneemovementinthespaceofthecentralpointsofthefemurandtibia.

Fig. 10 shows a polar graph representing the combined translationandrotationmovementsofthetibia,inrelation tothefemurduringkneeflexionandextension.

Discussion

The main contribution of this study is that it shows the viabilityofaprotocolformeasuringkneetranslationand rota-tion usingobjective and reproducibletools(error<0.2mm). Moreover, the technology that was developedfor correlat-ing betweenthe opticaland tomographic systemsand the computationalmethodologyfordescribingthemovementare Brazilianintellectualproperty.

Laneetal.10_{reportedthataclinicalgradingsystem} describ-ingkneestabilityintermsofkneeglide,kneeclunkingand

grossstabilityisvaluableforexperiencedorthopedists. How-ever,thissystemissubjectiveandnotreproduciblebetween surgeonsand,forthisreason,shouldnotbeusedinscientific studies.27

Themechanizedchallenge systemofthepivotshifttest isindependentoftheexaminerandalwaysallowsthesame angularvelocityandtraction of20Nthroughoutthe move-ment. Because the test is mechanized, this also reduces the risk ofbiasand increases theinternal validityofsuch studies.28 _{Consequently,thequality andrepresentativeness} ofthesestudiesarealsoincreased.

Anotherimportanttechnicalnoterelatingtothepresent methodology relates to the use of tomography for defin-ingthecenterofkneerotation.Thisselectioncanbemade after the end of the experiment and it is possible, for example, to define the translation of the tibia in relation

10

8

6

4

2

0

−2

0 20 40 60 80 100

Angle, ^o

120 140 160 180

Femur-tibia Tibia Femur

Time, s

−0.5

−1

0 1 2 3 4 5 6 7 8 9

Time, s

Intact Injured

Fig.9–Anteriortranslationofthetibiaaftertractionof68Nbymeansofametalpininthetibialtuberosity(after4s).Blue line–intactACL;redline–injuredACL.(Forinterpretationofthereferencestocolorinthisfigurelegend,thereaderis referredtothewebversionofthisarticle.)

to the femur, in the lateral, medial or intercondylar com-partments. Three-dimensional computed tomography also enablesreconstructionoftheknee inanyplaneandallows kneealignmentandcorrectmeasurementofthepositionsof thefemoralandtibialtunnels.29,30

Thepivotshiftphenomenon presentedinFig. 8is con-cordant with what was shown by Bull et al.,31 _{in which} subluxationofthe kneeoccurred atflexionofbetween25◦

and36◦_{.Otherstudieshavedemonstratedreductionofknee}

subluxationatflexionofbetween40◦_and44◦_.10

Onemethodological limitation ofbiomechanicalstudies relatestocarryingout experimentsattimezero,i.e. imme-diatelyafterthesurgicalprocedureforACLreconstruction.In ourstudyspecifically,becausenoligamentreconstructionwas performed,therewerenochangestothemechanical proper-tiesofgraftsduringanyperiodofbiologicalintegrationthat couldhaveinfluencedtheanalysisontheresultspresented.

Furtherstudiesaredesirable,inordertobiomechanically analyzetheknee withtunnelsindifferentanatomical pos-itions.Crossetal.32_{arguedthattherewasnoconsensusin}

Intact ACL Injured ACL

Extension Flexion

Translation [mm]

Axial rotation [

°]

5

4

3

2

1

0

0 2 4 6 8 10 12

Fig.10–Polarrepresentationofthecombinedtranslation androtationoftheknee.

theliteratureregardingwherewithintheoriginalfootprintthe ACLtunnelshouldbeconstructed.

Conclusion

Theclinical importanceofthepresent study relates tothe inferences thatcanbemade regardingthe invivobehavior ofknees withACL injuriesand the greater methodological qualitythatcanbeprovidedinfuturestudiesregarding mea-surements on surgical techniques with grafts in relatively closepositions.

Conflicts

of

interest

Theauthorsdeclarenoconflictsofinterest.

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